The overall goal of the proposed project is to investigate the degree and nature of neuropsychological and information processing impairments in siblings of schizophrenic patients. Recent neuroanatomical and neuropsychological research suggests that neuropsychological impairment is an important and promising candidate for the investigation of familially transmitted susceptibilities to schizophrenia. Aside from our pilot work, which appears encouraging, no family data are currently available on neuropsychological impairment along siblings of schizophrenic patients. The proposed study therefore seeks the following two specific goals. 1) To determine if neuropsychological all information processing impairments are familially associated with schizophrenia, in which case such impairments will be more common among siblings of schizophrenic patients than among controls. The potential overlap between neuropsychological impairments and clinically diagnosed schizophrenia spectrum disorders will also be examined to determine if neuropsychological impairments may represent a familially transmitted susceptibility to disorder that is sometimes independent of current overt symptomatology. 2) To investigate the origins of differences in neuropsychological and information processing functioning among schizophrenic patients by examining the aggregation of neuropsychological impairment in sibships of schizophrenic patients. These questions will be investigated using a sibling study design of 80 schizophrenic patient probands and their siblings (one randomly chosen sibling per proband) and 80 screened never mentally ill control probands and their siblings. All subjects will be comprehensively evaluated for neuropsychological impairment using a specially selected battery of standard tests that have been found to be sensitive to a range of brain pathologies among neurological patients. In addition, deficits on two well studied information processing tasks, the span of apprehension test (SAT) and the continuous performance test (CPT) will be measured. All subjects will also be systematically assessed for symptomatology, personality abnormalities, and functioning. The proposed study will thus be able to contribute in a unique way to several major questions in the field of research on schizophrenia.